Speaker
Mr
Wei Li
(Rice University (US))
Description
Various aspects of anisotropic collective flow in a system emerging in ultrarelativistic heavy-ion collisions have been studied by the method of two-particle correlations. A key assumption that is usually applied is that the Fourier coefficients of two-particle azimuthal distributions can be factorized into a product of single-particle anisotropy Fourier harmonics. Recent hydrodynamic studies indicate that due to the lumpy, fluctuating initial state, a pT-dependent event plane angle fluctuation will be induced, leading to a breakdown of the factorization assumption. Systematic study for this underlying effect is conducted using CMS data for 5.02 TeV pPb and 2.76 TeV PbPb collisions. Significant pT-dependent factorization breakdown in central PbPb collisions is observed. The data are compared to viscous hydrodynamic calculations with different initial-state conditions and eta/s values. Implication on constraining the transverse granularity of initial-state fluctuations using factorization data will be discussed. Furthermore, the effect of factorization breakdown for correlating two particles at different pseudorapidities will be discussed. This aspect of the measurement will provide important insight on the longitudinal dynamics of QGP fireball created in heavy-ion collisions.
